Effect of Accelerators on the Workability, Strength, and Microstructure of Ultra-High-Performance Concrete

The preparation of ultra-high-performance concrete (UHPC) with both high-early-strength and good workability contributes to further promotion of its development and application. This study investigated the effects of different accelerators (SM, alkaline powder accelerator; SF, alkaline powder accelerator containing fluorine; and AF, alkali-free liquid accelerator containing fluorine) on the workability and strength properties of UHPC. The microstructure of UHPC was also characterized by using XRD and SEM. Several dosage levels of accelerators (2%, 4%, 6%, and 8% by mass) were selected. The results indicate that the setting time and fluidity of UHPC are gradually decreased with an increase in accelerators dosage. Compared with fluorine-containing SF/AF, fluorine-free SM evidently facilitates UHPC early strength gain speed. However, the fluorine-containing accelerators have a higher 28 d strength ratio, especially AF. The maximum compressive and flexural strength ratios are obtained at a dosage of 6%, which are 95.5% and 98.3%, respectively. XRD and SEM tests further reveal the effect of different accelerators on the macroscopic properties of UHPC from the micro level.

Modeling of Casting Technology of Large-Sized Ingots from Deformable Aluminum Alloys

Industrial technology has been developed for the semi-continuous casting of large-sized ingots from deformable aluminum alloys through the use of complex modeling, including computer modeling and physical modeling. The ProCAST and ANSYS software packages equipped with the FLUENT module were used for computer modeling. The physical modeling was carried out on a laboratory semi-continuous casting unit (SCCU), which represents a tenfold reduced physical model of an industrial casting unit for the vertical semi-continuous casting of ingots from aluminum alloys. An aluminum-magnesium alloy with the addition of 0.05% (wt.) of scandium was used as the object of modeling. The results of computer modeling were tested at the SCCU, and then computer modeling was carried out for casting a large ingot. According to the modes obtained in the simulation, an ingot with a section of 1310×560 mm was cast under industrial conditions, which had a good surface quality with the absence of casting defects. In the microstructure of an industrial ingot and an ingot cast on the SCCU, there were no primary intermetallic compounds Al3(Sc, Zr), which makes it possible to strengthen the alloy upon annealing. To check the manufacturability during rolling, billets with a size of 40×120×170 mm were cut from these ingots, which were hot-rolled to a thickness of 5 mm, and then cold rolled to a thickness of 1 mm. The rolling results revealed good workability of the alloy, which was reflected in the high quality of the surface and the absence of cracks at the edges of the rolled stock. The mechanical properties of sheets obtained from both ingots were at the same level, which proves the reliability of casting modes for ingots obtained by complex modeling and the validity of their use for industrial conditions of the semi-continuous casting of large ingots from aluminum alloys.

Effect of Utilisation of Nano POFA on Performance of Self-Consolidating High-Performance Concrete (SCHPC)

Malaysia's palm oil industry plays a significant role in the country's economy. However, a large amount of palm oil fuel ash (POFA), a by-product of this industry, may negatively affect the environment and human health. Hence, this study hypothesized that POFA might be re-used in the form of replacement in concrete to lessen the risk to the environment or human health. Self-consolidating high-performance concrete (SCHPC) has been innovating progressively over the years. In this paper, SCHPC is innovated by utilising nano POFA (NaPOFA) to improve its performance. The POFA performance greatly improved when the particle size is reduced because the finer forms of POFA react effectively with the other constituent materials to produce stronger concrete. Hence this paper presents the experiment of the effect of utilisation of NaPOFA as a replacement to cement ranging between 0% and 10% to produce a self-consolidating high-performance concrete with good workability. The tests conducted were the flow table and compression test. The specimen used in the compression tests were 50 mm concrete cubes, tested in 1, 3, 7, 14, and 28 days. It was found that the inclusion of 1% POFA as a replacement to cement in concrete produced the highest compressive strength, 73.31 MPa, on the 28th day of testing. It was also found that its workability was as good as the control concrete. Thus, the utilisation of POFA could be considered environmental-friendly since it can be used as cement replacement and enhance the performance in terms of workability and strength.

Use of Palm Oil Clinker in Concrete Research: A Review

Palm oil clinker (POC) is a stone like by-product which is formed in the palm oil mill incinerator after extracted palm oil fibres and shells are burt to generate electricity for mill operation. The electricity is continuously generated. Then, the burnt fibres and shells are thrown at dumping areas as waste. This practice consumes a larger area at the landfills, causing environmental pollution. A review on the physical and chemical properties of POC was presented. The effect of using POC as lightweight aggregates and partial cement replacement on the mechanical properties of concrete produced was reviewed. The integration of suitable amount of POC as cement replacement and lightweight aggregates provided good workability and enhanced the concrete strength. Conclusively, this article has presented information regarding the development in POC concrete research, including the research gaps that remain to be filled.

Effect of Casting Temperatures and Curing Methods on Concrete Properties

This study concentrates on the effects of curing methods and casting temperatures on concrete properties in cases of fresh and solid states. The targeted strength of the concrete mix is 25 N/mm2. An experimental work was performed at the laboratory of the Faculty of Engineering, University of Khartoum. Initially the tests on the basic materials (cement, fine aggregate, coarse aggregate) used. The program was testing the strength of concrete for a number of 80 samples of three cubes and test for absorption of water for 16 samples. These samples were casted at temperatures of 15, 25, 35 and 50 c0 and cured with four different methods. Methods of curing used are immersing the samples in water, cured through the winding sample with Hessian and sprinkled water, winding samples with plastic sheets to prevent evaporation of water or loss of water from the sample and paint samples with doofagard. In addition some samples were uncured. The samples were broken in three days, seven days, 28 days and 56 days. In the water absorption tests the samples were casted at different temperatures and different methods of curing except a coating sample with doofagard because the sample cannot absorption water. Also the workability tests for the samples casted at temperatures 15, 25, 35 and 50 c0 were performed. The find out of these experimental works showed that: (1) the compressive strength of cement concrete specimens increased with the period of curing (2) curing of concrete by immersion in water results in a high compressive strength than the other methods of curing (3) The concrete will gain low compressive strength if it is not cured at all after casting (4) The best degree of casting temperatures is 15 and 25 c0 that resulted in a good workability and high compressive strength; on the other hand casting concrete at high temperature reduce workability of fresh concrete.

Durability properties of concrete made with polyethylene terepthalate and polypropylene as replacement of fine aggregate

Polyethylene Terephthalate (PET) and Polypropylene (PP) is mostly used materials for making items like water bottles, food containers and many other plastic products in all fields of life. Due to the scarcity of natural aggregates for making concrete, it is required to go for alternative material, this type of plastic is one of the materials for replacement of fine aggregate in concrete. An objective of this paper is to study the feasibility of this recycled PET and PP plastic waste to be used as a building material in manufacturing of concrete which is replaced in fine aggregate. Polyethylene Terephthalate and Polypropylene is used in various percentages like 5%, 10%, 15% and also various tests like workability and compressive strength, Sorptivity, water absorption, acid attack and sulphate attack tests are conducted. From the results the PP shows good workability but low compressive strength than PET. From the durability point of view, the concrete made with PET and PP have given better results compared to conventional concrete of M30 grade. In PET and PP concrete, PET resists the acid, sulphate and water over the long period much better than the PP. So, PET can be replaced up to 10% in fine aggregate, whereas PP is allowed up to 5% replacement of fine aggregate.

A method for replacing lower flange splice plate of a steel I-girder connection using BPL

<p>In recent years, corrosion damages of the steel I-girder bridge joints have been reported. With the increasing demand for the replacement of splice plates of the damaged joints, good workability without using temporary supports is required when considering the cost and time necessary to execute such works. In the present study, FEM analysis has been conducted in order to propose a new replacing method for the lower flange splice plates in steel I-girder, which uses a bypass device of steel plate named BPL that is attached to the web panel. From the analytical results, it has been confirmed that using the BPL and replacing the lower flange splice plates, the stress at the lower flange splice plates is transferred to the BPL and redistributed to the new lower flange splice plates after the removal of BPL. It has also been clarified the geometrical configuration of the BPL that can reduce the stress at the web effectively during replacement of the lower flange splice plates.</p>

CARTECH Ti-3Al-8V-6Cr-4Mo-4Zr (BETA C)

CarTech Ti-3Al-8V-6Cr-4Mo-4Zr, also known as Ti-3-8-6-4-4 and Beta C, is a metastable beta alloy used in the solution heat treated or solution heat treated and aged condition. It is appropriate for applications where very high strength, minimum weight, and corrosion resistance are important. Ti-3Al-8V-6Cr-4Mo-4Zr has gained in popularity among beta alloys because it is easier to melt and process, exhibiting low segregation, good workability, and good heat-treating properties. This datasheet provides information on composition, physical properties, elasticity, and tensile properties. It also includes information on corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: Ti-172. Producer or source: Carpenter Technology Corporation.

Waste of Civil Construction for Use in Mortar and Production of Structural Concrete

Civil construction is a sector of extreme impact on the Brazilian economy, both in terms of jobs as well as consumption of raw material and waste generation. Civil construction waste (CCW) represents a large part of the total mass of municipal solid waste in a medium and large city. An alternative to diminish these released wastes is to reuse them. In this work, a study was carried out using CCW both to produce concrete with sand substitution and as a small aggregate for use in mortar. The compression strength of structural concrete and mortar, with total and partial replacement of sand, was analyzed. In addition, the consistency of mortar with the replacing was also studied. The results of the compression test indicate superior quality for concretes (75wt% CCW) and mortar with CCW incorporation. The required amount of water for good workability in the modified mortar is 310 g, against 270 g for the reference mortar.

Sustainable Development and Performance Evaluation of Marble-Waste-Based Geopolymer Concrete

The key objective of this study was to develop marble-based geopolymer concrete and examine the viability of its application as a sustainable structural material for the construction industry. The results of the research demonstrated that marble-based geopolymer concrete can be developed, and its physical/mechanical properties were shown to have a very good performance. According to various experimental tests and a large-scale ready-mixed plant test, it was found that the marble-based geopolymer concrete displayed a good workability and was not easily influenced by temperature changes. The results showed that marble-based geopolymer concrete has an excellent potential for further engineering development in the future.